Gyratory Compactor Research Articles

Real-Time Optimization of Discrete Element Models for Studying Asphalt Mixture Compaction Characteristics at the Meso-Scale

To enhance the quality of asphalt mixture compaction, the compaction mechanism, particularly at the meso-scale, must be thoroughly understood. Researchers have employed various technologies to study the compaction process. Among these, discrete element modeling (DEM) has been widely adopted due to its effectiveness in addressing particle-scale problems. However, improving simulation accuracy while maintaining computational efficiency remains a challenge. Therefore, this study aims to establish and optimize a DEM model for asphalt mixture gyratory compaction by integrating real-time laboratory SmartKli® sensing data. The Kalman filter was implemented as the fusion algorithm to enable real-time calibration. Two SmartKli sensors were positioned at different locations within specimens during both the laboratory Superpave gyratory compaction (SGC) test and DEM simulation to investigate the particle rotation characteristics. The results showed that the upper layer exhibited a higher degree of compaction than the lower layer. After calibration, particle rotation in the optimized DEM model more closely matched the laboratory SmartKli sensing data. Additionally, the changing trends of relative rotation for both SmartKli particles and coarse aggregate particles improved. The SmartKli simulation ball effectively represented the rotational behavior of its surrounding coarse aggregates, making its kinematic responses a reliable predictor of asphalt mixture compaction characteristics at the meso-scale.

MIX DESIGN AND LABORATORY COMPACTION METHODS OF RCCP – A REVIEW

This article analyzes the difficulties in reproducing the actual circumstances of concrete compaction with rollers in the laboratory and mix design аfeatures of RCCP (Roller Compacted Concrete Pavement). While quick and straightforward, the Proctor compaction test may not adequately reflect the field compaction achieved with rollers. Gyratory compactors simulate the movement of the rollers, providing a more realistic situation with greater accuracy. However, they are expensive and require specialized knowledge. Due to the Vibratory hammer limited application and unrealistic vibration pattern compared to rollers, it is mostly used in laboratories for sample preparation rather than compaction. A vibrating table is effective for less rigid RCC mixture combinations and provides good compaction, although it does not perfectly simulate the action of a roller. The paper also underlines the need to create a link between density and moisture content to achieve maximum RCC performance.

Gyratory compactor and mixture volumetric evaluation of roller-compacted concrete for pavement constructability

Standard roller-compacted concrete (RCC) test methods such as the modified proctor, Vebe, and vibratory hammer are used to determine final mixture proportions, evaluate consistency, and prepare cylindrical specimens for strength. However, these methods do not replicate the method and levels of compaction observed in the field and require multiple iterations to find a constructable and sustainable RCC mixture for pavements. Better linking RCC compaction properties with mixture volumetrics can enable more efficient RCC constituent selection and proportions. For this research, a typical RCC pavement mixture was selected from which the aggregate voids filled by paste (VFP) varied six levels to achieve mixtures ranging from underfilled (VFP=63.4 %) to overfilled (VFP=126.9 %). A gyratory compactor with a vertical and torque load cell was employed to continuously measure the compaction energy evolution in each specimen and for all mixtures. The volumetric compaction energy required to reach 90 % of the absolute density (Einitial0−90) and incremental energy to compact 90–95 % absolute density (Efinal90−95) was determined and used to evaluate RCC paveability and compactability, respectively, and relate it to mixture volumetrics. All RCC mixtures were able to achieve the initial density but at least equifilling was required to achieve final density under reasonable energy levels (≤ 2.70 MJ/m3), with compaction energy decreasing exponentially as the VFP increased. The gyratory compactor more efficiently compacted the reference mixture (VFP=117.9 %) to the same density as the modified proctor test (1.88 vs 2.70 MJ/m3) or cylinders with the vibratory hammer (3.10 vs 10.0 MJ/m3). The gyratory compactor with a perforated mold also enabled quantification of paste mobility within the aggregate skeleton. The time needed for initial and final seepage through the mold perforations was better and more sensitive than the Vebe and vibratory hammer compaction times, with seepage times ranging from 5 to 166 seconds for RCC mixtures from overfilled to underfilled. The perforated mold and a wet sieve analysis also allowed for experimental determination of intergranular voids (IGV) and total paste volume (TPV) of the RCC mixtures, respectively, which had an average relative error of 3.4 % and 4.0 %, respectively.

Compaction Evolution and Mechanisms of Granular Materials Due to Gyratory Shearing.

Granular systems, no matter whether they are dry or saturated, are commonly encountered in both natural scenarios and engineering applications. In this work, we tackle the compaction problem of both dry and saturated granular systems under gyratory shearing compaction, where particles are subjected to constant pressure and continuous shear rate, which is quite different from the traditional cyclic shearing compaction. Such phenomena are crucial to the compaction of asphalt mixtures or soils in civil engineering and can be extended to other areas, such as powder processing and pharmaceutical engineering. In this study, we investigated the behavior of both dry and fully saturated mono-dispersed granular materials under gyratory shearing compaction using the discrete element method (DEM) and found that the gyratory speed or interstitial fluid viscosity has almost no impact on the compaction behavior, while the pressure and the particle size play more important roles. Additionally, it is the inertial time scale which dictates the compaction behavior under gyratory shearing in most cases; meanwhile, the viscous time scale can also have influence in some conditions. This work determines the similarity and unity between the granular gyratory compaction and the rheology of granular systems, which has direct relevance to various natural and engineering systems.

Crack Resistance by Semi-Circular Bending Test and Gyratory Compaction of High Fraction RAP in Warm Mixed Asphalt Mixtures

Crack Resistance by Semi-Circular Bending Test and Gyratory Compaction of High Fraction RAP in Warm Mixed Asphalt Mixtures

Performance assessment of sustainable asphalt concrete using steel slag, with an artificial neural network prediction of asphalt concrete behavior

This research evaluated the possibility of using Moroccan steelworks slag as a substitute for natural aggregates in asphalt mixtures, using chemical and mechanical analyses to demonstrate its compatibility with this application. Two granular mixtures, M1 and M2, were developed, incorporating respectively 15 % and 25 % natural sand (0/1.25) with slag aggregates to obtain granular mixtures complying with local standards. These mixtures were then tested with three different asphalt contents (4.7 %, 5.2 %, and 5.7 %). Mechanical tests, including a gyratory compactor, Marshall stability, and Duriez strength, were carried out. In particular, the M1:5.2 and M2:5.2 mixtures met compaction criteria and showed remarkable Marshall Stability values, reaching 23.49 kN and 21.81 kN respectively. In comparison, the control mixtures only achieved a maximum stability of 11 kN. Thermal properties were also assessed, showing that the maximum thermal conductivity was achieved at an asphalt content of 5.2 %. The slag-based mixtures, M1 and M2, showed higher thermal conductivity than the control mix M0, with maximum values of 0.74 W/mK for M1 and 0.86 W/mK for M2, compared with 0.56 W/mK for M0. The overall results show that the M1 and M2 mixtures had improved thermal and mechanical properties compared with the M0 control mix. Artificial neural network (ANN) modelling was carried out using Marshall Test data. It showed excellent performance in predicting the stability and flow properties of asphalt mixtures. These results suggest that incorporating steelmaking slag into asphalt concrete mixtures was an effective strategy for simultaneously improving their thermal and mechanical properties.

A SmartRock-Based Method for Determining the Gyratory Compaction Locking Point of Asphalt Mixture

A SmartRock-Based Method for Determining the Gyratory Compaction Locking Point of Asphalt Mixture

Random distribution of asphalt and cement mortar in semi-flexible pavement: Implication for cracking resistance

The distribution characteristics of asphalt and cement mortar play a crucial role in determining the cracking resistance of semi-flexible pavements (SFP). In this study, digital image processing technology was utilized to quantify the thickness distribution of asphalt and cement mortar within SFP, and a parallel line segmentation method was employed to characterize the random distribution of mortar thickness (RDMT) of asphalt and cement mortar. Variance, coefficient of variation (COV), and interquartile range were proposed to characterize RDMT, examining the effects of air voids (AV) content, nominal maximum aggregate size (NMAS), and compaction method on RDMT, and its variation along the specimen height. Semi-circular bending test was conducted to evaluated the cracking resistance of SFP, exploring the relationship between RDMT and cracking resistance. Results indicate that parallel line segmentation method with 36 parts and 25 parts is recommended to characterize the RDMT of asphalt and cement mortar, respectively. An increase in AV content led to a higher RDMT for asphalt mortar but a lower RDMT for cement mortar. Conversely, as NMAS increased, the average thickness of asphalt and cement mortar increased, while the RDMT of asphalt mortar decreased and that of cement mortar increased. RDMT of asphalt and cement mortar is higher under Superpave gyration compaction method compared to the Marshall compaction method. Additionally, RDMT increased from the top to the bottom of the specimen height. Based on the RDMT, a random distribution index (RDI) was proposed, which exhibited a strong linear relationship with the cracking resistance of SFP. When the RDI decreased by 44.4 %, the corresponding cracking resistance of SFP increased by 84.0 %. Improving the distribution of asphalt and cement mortar could enhance the cracking resistance of SFP.

Effect of Production and Curing Methods on the Properties of Roller-Compacted Concrete: A Review

Roller Compacted Concrete (RCC) exhibits many characteristics of both asphalt and rigid pavements, but their use is restricted. Many reasons led to this decision, including the fact that RCC is a type of concrete mixture that requires a specific consistency. It should be firm enough to be compacted by a roller compactor but also have enough moisture to ensure even distribution. The lab-field performance difference of RCC is another reason for decreasing its use. The laboratory RCC mixes are prepared using the modified Proctor compaction method. Subsequently, specimens are fabricated utilizing a vibratory hammer (VH) to evaluate their strength properties. Nevertheless, in the construction industry, pavement is built utilizing static, pneumatic, and vibratory rollers. Consequently, quality control is carried out by acquiring pavement samples and comparing them to laboratory samples. Each of these procedures employs different processes and energies, resulting in variations in field and laboratory behavior. In this investigation, some studies will be discussed about the RCC behavior under field and lab conditions using various design methods, such as the vibrating table (VH), vibratory table (VT), gyratory compactor (GC), and modified proctor (MP). These studies showed a difference in RCC mechanical and macroscale properties between laboratory compaction methods. For instance, VH specimens led to a higher evaluation, while GY specimens produced a less favorable estimation of the hardened properties observed in the field. While the MP and VT compacted specimens had a comparable structural arrangement to the field, they exhibited notable differences in terms of porosity and strength. Other studies revealed the essence of the curing stage in terms of RCC mechanical properties and indicated that some curing processes, like compound curing, may improve RCC performance.

An alternative approach for increasing the visibility of roads

Visibility problems occur on highways that are not sufficiently illuminated at night, endangering traffic safety. Phosphor material, which has a natural glow feature under ultraviolet (UV) light, is planned to increase road visibility in areas with inadequate lighting. Phosphor powder (PP) was used in four different percentages (25%, 50%, 75%, and 100%) as fillers in hot mix asphalt (HMA), reduced to filler size. Asphalt specimens were prepared using a super pave gyratory compactor and super pave volumetric mixture design. Compacted specimens were exposed to artificial 12V UV light for 10-minute intervals in a dark room, and UV light absorption was observed. Visibility analyses were performed on the specimens by taking high-resolution photos with long exposure from a distance of approximately 30 cm from the asphalt specimen using a professional camera. According to the analysis results, the visibility values increased by 200.4%, 378.5%, 538.1%, and 728.5% compared to the reference specimen for substitution rates of 25%, 50%, 75%, and 100%, respectively. Experiments were conducted to determine the behavior of the specimens prepared as phosphorus substitutes in the mixture. After selecting the optimum binder contents, the modified Lottman test procedure was applied to measure the specimens' strength values and moisture sensitivity prepared at optimum ratios. The indirect tensile test results show that the 25% PP-substituted specimen had a better strength value. The tensile strength ratio (TSR) value, the ratio of dry and wet tensile stresses, was determined to have minor moisture sensitivity in the 50% PP-substituted specimen. HWTT was applied to the specimen containing 50% PP content, which exhibited the best TSR ratio, resulting in improved rutting performance compared to the reference specimen.

Aggregate uniformity of recycled asphalt mixtures with RAP from refined decomposition process: Comparison with routine crushing method

In consideration of skyrocketing price in pavement materials and ever-increasing attention to environment preservation, the utilization of reclaimed asphalt pavement (RAP) into asphalt mixtures has gained more and more favor. However, the uniformity of virgin and RAP aggregate in recycled asphalt mixtures (RAM) has not yet been studied due to the difficulty in informational extraction of multi-structures. To address this, white dolomite was used as virgin aggregate to be distinguished from RAP aggregate based on their color difference. The shear gyratory compactor specimens of RAM were prepared and saw-cut, and then meso-structures including virgin aggregate, RAP aggregate and asphalt mortar were extracted using digital image processing (DIP) technology. The DIP processes mainly involved retention of blue channel for image graying, newly proposed double-threshold OTSU method for image segmentation and image morphology processing. The aggregate uniformity index (AUI) was proposed based on the coefficient of variation of aggregate area ratio. The influences of RAP that were pre-processed by refined decomposition (RD) and routine crushing (RC) and its content on the aggregate uniformity were evaluated. The results demonstrate the efficacy of the improved DIP approach, as evidenced by the maximum mean absolute error between laboratory-measured and image-estimated gradation that is lower than 7.8 %. The addition of RAP into asphalt mixtures is adverse to the aggregate uniformity. The higher the RAP content, the inferior the aggregate uniformity of RAM, which attributes to the agglomeration of RAP materials. RAP agglomeration leads to the heterogeneity of RAP aggregate and thus dominates the heterogeneity of the whole aggregate. Therefore, the aggregate uniformity of RAM produced by RD-RAP is superior to that produced by RC-RAP. The superior degree is 9 %.

Compaction method and specimen geometry effect on the fracture properties of asphalt concrete in the SCB test at intermediate temperature

ABSTRACT Recent research using the semicircular bending (SCB) test with 100 mm diameter specimen cored from gyratory compacted samples demonstrated the suitability of this sample size for testing dense graded asphalt mixes with a nominal maximum aggregate size (NMAS) of up to 19 mm. Alongside the gyratory compactor, the Marshall compactor remains part of current specifications in many countries, including ASTM international standards. The Marshall compactor uses a 4-inch (101.6 mm) mould, which is slightly larger than the gyratory compactor’s 100 mm mould, and employs a different compaction effort, resulting in different aggregate orientation. This study investigates potential differences in the fracture properties of SCB test specimens compacted using different methods. Sample thicknesses of 30 , 40 , and 50 mm were evaluated in the SCB test at 25°C under a monotonic loading rate of 1 mm/min. A total of 81 specimens were prepared from three asphalt mixes with NMAS of 14 mm and 20 mm, including two dense graded asphalt mixes and one stone mastic asphalt mix. The fracture properties, including fracture energy, fracture toughness, and cracking resistance index (CRI) were evaluated. The study found that the repeatability, evaluated via the coefficient of variation, ranged from 1.1% to 21.7%, with an average value of 8.3%. A directly proportional relation was observed for indexes from the 100 mm and 150 mm samples using the gyratory compactor. The Marshall compactor specimens yielded higher fracture toughness and fracture energy values, while the CRI values were approximately 1.23 times those obtained from the gyratory compactor. This result shows that different compaction methods have direct effect on the fracture properties of SCB test specimens, emphasising the importance of considering compaction methods for the SCB test when determining the threshold value of cracking resistance for asphalt mixes, especially in the balanced mix design for asphalt mixes.

Study on the Road Performance and Compaction Characteristics of Fiber-Reinforced High-RAP Plant-Mixed Hot Recycled Asphalt Mixtures.

Recycled asphalt pavement (RAP) mixtures are widely adopted due to their significant economic and social benefits from utilizing pavement recycling materials. This study incorporates basalt fibers (BF) and polyester fibers (PF) into plant-mixed hot recycled asphalt mixtures to analyze their enhancement effects on the high-temperature, low-temperature, and fatigue performance at different RAP content levels. Additionally, the study investigates the impact of fiber and RAP additions on the compaction characteristics of the mixtures using gyratory compaction tests, aiming to increase the RAP content of plant-mixed hot recycled asphalt mixtures. Experimental results demonstrate that at 30% and 50% RAP content levels, basalt fibers exhibit more pronounced enhancement effects on the performance of recycled asphalt mixtures compared to polyester fibers. Incorporating basalt fibers increases the fracture energy of recycled asphalt mixtures by 8.63% and 13.9%, and improves fatigue life by 154% and 135%, respectively. Moreover, the addition of both types of fibers increases compaction difficulty, with polyester fibers showing a more significant influence on the compaction energy index (CEI).

Evaluation of Bio-Rejuvenator and Compaction Conditions on Stiffness Modulus and Indirect Tensile Strength of Recycled Hot Mix Asphalt.

This study focuses on the investigation of the effect of a reclaimed asphalt material (RAP) and a bio-rejuvenator (mix of vegetable oils) on the stiffness modulus and indirect tensile strength (ITS) values of eight bituminous mixtures produced by using three types of compaction, with different RAP amounts (25% and 50%) and rejuvenator (0%, 0.20%, 0.40% and 0.60% by mass of RAP). A conventional hot mix asphalt was considered as the reference mix. All tests were performed on cylindrical samples produced using: Marshall compaction with 50 blows/side, cored cylindrical specimens from slabs compacted using a roller compactor (39 passes), and, respectively, gyratory compaction on 80 gyrations. Stiffness modulus and ITS values showed strong linear variation with the increase in rejuvenator content, independently of test temperature and type of compaction. The rejuvenating effect of the bio-rejuvenator was observed to counterbalance the impact of RAP. The results at 20 °C for gyratory specimens for the mix with 50% RAP and 0.40% bio-rejuvenator were comparable/closer (under 5% relative difference) to those obtained for the reference mix. A strong correlation between stiffness modulus values of mixes and penetration values of the corresponding binder blends was obtained (R2≥0.977).

New hot-mix cold-laid mix design method with a superpave gyratory compactor

This study introduces a novel method for designing Hot-Mix Cold-Laid (HMCL) asphalt mixes, which are essential for pavement maintenance. In Texas, the current practice for HMCL mix designs adheres to the traditional Hveem method, employing a Texas Gyratory Compactor (TGC) in line with the Texas Department of Transportation (TxDOT) specifications. However, this research advocates for the use of a Superpave Gyratory Compactor (SGC), a more advanced and modern alternative. The SGC, widely used for Hot-Mix Asphalt (HMA) mix designs, provides more adjustable parameters and the ability to control compaction densities. Five types of industrial-based HMCL mixes were examined, each type having three levels of binder content. These fifteen laboratory-mixed HMCL mixes were used to mold SGC specimens at four compaction levels. This established the design gyration for SGC lab-molded densities within 94.0 ± 1.5 %. The investigation revealed that the existing specification might include mix designs with low compactability and weak correlations with field performance, due to their insensitivity to binder contents. The proposed method uses Cantabro mass loss test, IDEAL cracking test, and rutting test to characterize mix resistance to raveling, cracking, and rutting. The binder contents significantly affected these test results, leading to the exclusion of mixes with low compactability during testing. Thus, the new HMCL design method using an SGC enhances the current method.

Susceptibility to moisture damage in asphalt mixes with blast furnace dust as aggregate

One of the ongoing challenges in engineering is mitigating the degradation of road infrastructure caused by water in asphalt mixes. This study aims to assess the impact of blast furnace dust, a byproduct of the steel manufacturing process, on moisture-induced damage in asphalt mixes. Three asphalt mixes were developed following the Marshall methodology: one comprising conventional crushed aggregates, while the others substituted 50% and 100% of the conventional fine aggregate with blast furnace dust. Material characterization procedures and chemical analysis of the blast furnace dust were conducted. Once compliance with the specified material requirements was verified and analyzed, water susceptibility was evaluated through an indirect tensile test across various void content levels. Similarly, leveraging the Superpave gyratory compactor, several compaction indices were determined to estimate the compaction behavior of each mix. Based on the findings, the inclusion of blast furnace dust in an asphalt mix proved satisfactory due to its contributions in enhancing tensile strength, consequently leading to a reduction in moisture-induced damage within the asphalt mix, as well as exhibiting improved compaction behavior. Additionally, this utilization contributed to diminishing the environmental impact linked to the steel production process, where substantial quantities of this residue accumulate.

Compaction and shear characteristics of recycled construction & demolition aggregates in subgrade: Exploring particle breakage and shape effects

Recycling construction and demolition (C&D) wastes into useable aggregates in subgrade applications offers significant sustainability benefits. However, the characteristics of recycled aggregates, including particle morphology, crushing strength, and shear behavior, differ substantially from natural aggregates. This paper presented an extensive experimental study on the compaction and mechanics performances of recycled concrete and brick aggregates, with a particular focus on the effects of particle breakage and shape characteristics. The compaction of recycled aggregate specimens comprising three structural types was evaluated using heavy Marshall compaction (HMC) and Superpave gyratory compaction (SGC). The compaction characteristics and particle breakage were examined, enabling a profound understanding of the compaction mechanisms associated with both methods. Furthermore, triaxial shear tests were performed to scrutinize the influences of particle shape, compaction degree, and confining pressure on shear characteristics. Results showed that after 80 gyratory rotations in SGC, the compaction degree of recycled aggregates aligned with the targeted results obtained from HMC. Changes in fractal dimension after compaction exhibited direct correlations with the two-dimensional shape distribution. Axial coefficient, fractal dimension and confining pressure most strongly influenced shear strength. In light of these insights, prediction models for shear strength parameters were proposed using multiple regression analysis. Overall, the study provides valuable insights into the relationships between aggregate morphology, compaction response, breakage behavior, and shear performance. These findings can facilitate optimized design and construction using recycled aggregates to advance sustainable infrastructure development.

Sensitivity analysis of gyratory compactor variables to mimic roller compacted concrete pavement performance

ABSTRACT The compaction parameters suggested for Superpave gyratory compactor by ASTM C1800 are primarily derived from the asphalt mix (ASTM D6925). Since the rheological behaviour of Roller Compacted Concrete Pavement (RCCP) is significantly different from asphalt mixes, conventional Superpave compaction parameters cannot be directly adopted for RCCP. Hence, the current study focuses on formulating compaction parameters for the design of RCCP to resemble the field behaviour. For this task, response surface methodology was employed to investigate the effect of gyratory compactor parameters such as internal angle (0.82–3°), compaction pressure (600–1000 kPa), and gyration levels (60–120) on the performance of RCCP specimens. The accuracy of the response prediction model was verified with ANOVA analysis. Further, multiobjective optimization was performed and validated with experimental findings. For validation of laboratory findings, a field test section was constructed using a duplex roller (dual drum vibratory roller). The results showed that the ASTM C1800 suggested gyratory parameters resulted in lower fresh density and strength properties of 4% and 7–45%, respectively, than the field specimens. However, the specimens fabricated at 1.92° internal angle, 120 gyrations, 1000 kPa, and 1 aspect ratio in the gyratory compactor could provide comparable field properties.

Analysis of the compactibility of bituminous mixtures for reflective crack relief interlayers (RCRI)

The physical properties determining the strength parameters of bituminous mixtures are strongly influenced by the processes of placement and compaction. The effectiveness of this process depends on the compactive effort and is directly related to the mixture temperature. This research focused on the assessment of compactibility of mixtures designed for reflective crack relief interlayers (RCRI) which, in most cases, are applied in thin layers. The materials analysed for compactibility in this research included AC – asphalt concrete, AC AF – asphalt concrete “anti-fatigue”, SMA – stone mastic asphalt and SMA-MA – stone mastic asphalt rich in bitumen mastic. The gyratory compactor method was used to determine the compaction slope K, the locking point LP and the compaction densification index CDI. All the tested mixtures were fine-graded, i.e., contained grains up to 8 mm in diameter, each mixed with a different type of bituminous binder. The values of CDI show a substantially greater input of energy required for compaction of high-polymer modified mixtures, as compared to mixtures of the same design, yet containing the 50/70 bitumen. Locking point analysis showed that SMA and SMA-MA mixtures attain 98% relative compaction before reaching the locking point at which the aggregate skeleton starts to resist further compaction. This is quite the opposite as with the AC and AC AF mixtures. Among the tested mixtures the best compaction behaviour was observed in the case of SMA-MA 8 50/70, and this over a wide range of working temperature (100–160C°) and pressures (150 kPa, 600 kPa). The design of the mixture SMA-MA as an anti-fatigue layer assumes an increase in the content of filler and binder, as compared to conventional SMA. This composition is bound to reduce the resistance to compaction, i.e., provide a better compaction behaviour as compared to a conventional SMA mixture.

The Friction-Lubrication Effect and Compaction Characteristics of an SMA Asphalt Mixture under Variable Temperature Conditions.

The aim of this article is to explore the dynamic compaction characteristics of stone mastic asphalt (SMA) and the friction-lubrication effect of internal particles during the superpave gyratory compaction (SGC) process. Firstly, a calculated method for the compaction degree of an asphalt mixture in the gyratory compaction process was defined based on the multiphase granular volume method. Secondly, the gyratory compaction curves of asphalt mixtures were taken based on this calculation method of compaction degree. The dynamic change law of each compaction index (compaction, percentage of air voids, compaction energy index, etc.) during the compaction process was analysed. Finally, the effects of different initial compaction temperatures and different asphalt content on the friction-lubrication effect and compaction characteristics of asphalt mixtures were studied. Research shows that it is reasonable to define the compaction degree by the ratio of the apparent density of the asphalt mixture to the maximum theoretical density of the asphalt mixture during gyratory compaction. The dynamic prediction equations of the compaction degree K and the compaction energy index CEI with the amount of compaction were established, and could effectively predict the compaction degree, percentage of air voids and compaction energy index CEI. The compaction process of the asphalt mixture needed to go through three phases, including periods of rapid growth, slow growth, and stabilisation, and the compaction degree increased by about 10%, 5%, and 1%, in that order, finally tending towards a stable value. The effect of the initial compaction temperature on the forming compaction degree of the asphalt mixture is significant; therefore, it should be controlled strictly in the compaction construction of asphalt mixtures. When the initial compaction temperature of SMA-13 is about 170 °C, the compaction effect is optimal, and the effect of the increase in the amount of compaction at a later stage on the increase in the compaction degree of the asphalt mixture is very low. With the optimal asphalt content, the friction-lubrication effect between the asphalt and aggregate particles is optimal, because it can effectively form an asphalt film, reducing the frictional resistance of the particles moving each other during the compaction process, and the voids will be embedded and filled with each other, finally producing the best compaction result.